The invention relates to synchronization of a digital receiver in a manner which is tolerant of data rate errors.
For data transmission, a distinction is drawn between synchronous and asynchronous transmission. In the case of synchronous transmission, the clock generators of the transmitter and the receiver are in sync with one another. In the case of asynchronous transmission, the clock generators of the receiver and the transmitter nominally provide the same frequency but run independently of one another. This means that an at least small frequency difference is inevitable.
Even with asynchronous transmission, the receiver must be able to identify when useful data are applied to the input of the receiver. This is done by using synchronization. A frame which is to be transmitted therefore includes a preamble and useful data. The preamble is used by the receiver to identify the start of a new frame.
To identify the preamble, U.S. Pat. No. 7,003,063 involves the production of a modulated reference signal which corresponds to an expected modulated preamble. By correlating the reference signal to a received signal, it is established whether a preamble has been transmitted. However, such a method is susceptible to fluctuations in the data rate, which can result in transmission errors.
For these and other reasons there is a need for the present invention.